Republican presidential hopeful Mitt Romney said Thursday night that US President Barack Obama "threw Israel under the bus" by designating the pre-1967 borders as a starting point for peace talks, while Newt Gingrich reiterated his controversial remark that the Palestinians are an "invented" people.

Speaking at a CNN Republican debate in Florida ahead of Tuesday's primary, the two candidates skewered Obama for not being a strong enough ally to Israel.

During his State of the Union address on Tuesday, Obama touted his credentials on Israel, indicating his efforts to impose tough sanctions on Iran and saying, "Our ironclad commitment to Israel's security has meant the closest military cooperation between our two countries in history."

The candidates' statements came in response to a question from a Palestinian-American audience member (who specified that he was also a Republican: "We exist," he said).

Both Romney and Gingrich blamed the Palestinian leadership for lack of progress in peace negotiations with Israel.

"There's the belief that the Jewish people do not have a right to a state" Romney said of Palestinians, offering Hamas's presence in the Palestinian government, schoolbooks that advocate killing Jews and rejectionist political discourse by Fatah as examples.

Gingrich said his goal was for Palestinians to live in peace with Israel, and that "they can achieve it any morning they say Israel has a right to exist."

The former speaker of the House noted that 11 rockets were fired at Israel in November. "How many of you would be for a peace process and how many would say 'that looks like an act of war?'"

While Romney promised "I will stand with our friend Israel," if he were elected president, Gingrich promised to issue an executive order moving the US embassy from Tel Aviv to Jerusalem on his first day in office.